Noob Question: Symmetrized my bones, but Weight Painting is still mirrored?
The mesh object does not have enough vertex groups for the deformed bone names.
The results of searching with the keyword &quot;Lip&quot; are shown in the Vertex Groups List in the figure.
Select Mesh Object, then Armature in Object Mode. Press the Ctrl+P key and select With Empty Groups.

PS: Lip2C.L is a non-deformed bone name and can be removed from the list.